2023 Annual International Solid Freeform Fabrication Symposium (SFF Symp 2023): Process Development: Powder Bed Fusion Process Innovations
Program Organizers: Joseph Beaman, University of Texas at Austin
Tuesday 8:15 AM
August 15, 2023
Room: 404
Location: Hilton Austin
Session Chair: Venkatavaradan Sunderarajan, Georgia Institute of Technology
8:15 AM
Layer-wise Control Charts in Laser Powder Bed Fusion Metal Additive Manufacturing: Venkatavaradan Sunderarajan1; Suman Das1; 1Georgia Institute of Technology
Implementing robust statistical process control will address many challenges that prevent widespread industrial adoption of Laser Powder Bed Fusion (LPBF) Metal Additive Manufacturing. Presently, vast amounts of heterogeneous data from multiple in-situ monitoring sensors capture process information in real-time across length and time scales. This work demonstrates an effective method to parse and analyze this data, extract valuable information, and apply multivariate statistics to develop control charts for monitoring the LPBF process. This will enable a direct approach to layer-wise monitoring of the build, to track and quantify process variations across builds on the same machine and also compare performance across machines. Post-build part characterization helps establish correlations between the part properties and process state measured in-situ. Appropriate process control measures and critical limits can then be implemented for each process variable (or any combination), commensurate with the tolerance in part property allowables depending on the end-use application.
8:35 AM
SmartScan Extension: Enhancing Temperature Uniformity in 3D Laser Powder Bed Fusion Additive Manufacturing for Reduced Part Defects and Distortions: Chuan He1; Nevzat Bugdayci1; Chinedum Okwudire1; 1University of Michigan
Laser powder bed fusion (LPBF) additive manufacturing often faces part defects due to non-uniform temperature distribution during fabrication. To address this, the authors previously introduced SmartScan, an intelligent method utilizing modeling and optimization to generate scan sequences enhancing temperature uniformity. However, its application was limited to single layers. This work extends SmartScan to three-dimensional parts by modifying the thermal model and optimization objective. Through simulations and experimental fabrication of AISI 316L stainless steel parts, the study demonstrates that the proposed SmartScan approach substantially improves temperature uniformity, diminishes part distortion, and alleviates residual stress when compared to conventional heuristic sequences.
8:55 AM
Toward Voxel Level Control for Laser Powder Bed Fusion Additive Manufacturing Process: Ho Yeung1; Jorge Neira1; 1National Institute of Standards and Technology
In the Laser Powder Bed Fusion (LPBF) additive manufacturing (AM) process, a high-speed scanning laser beam is employed to construct components by melting and fusing metal powder together. While AM is generally characterized as a layer-by-layer technique, LPBF actually builds parts on a voxel-by-voxel basis (utilizing a point laser heating source). As a result, managing the LPBF process at the voxel level – that is, focusing on individual 3D printing elements or volume pixels – will be highly beneficial. In this study, we will explore the laser control requirements necessary for achieving voxel-level precision in the LPBF process and demonstrate these concepts through experiments.
9:15 AM
Enabling Multi-material LPBF Printing via Electrostatic Powder Spreading of Patterned Powder Beds: Eric Elton1; Michael Troksa1; Ziheng Wu1; Gabe Guss1; 1Lawrence Livermore National Laboratory
Laser powder bed fusion processes typically rely on mechanically spreading each powder layer with a spreader bar, limiting the ability to deposit multiple materials on one layer. While methods to deposit more than one powder per layer exist, they are complicated and time consuming. Here we use electrostatic powder spreading (ESPS) to deposit multiple metal powders on a single layer and build multi-material LPBF parts. ESPS uses the electric field between a powder reservoir and an electrode to move powder from the reservoir to the powder bed. By using an array of electrodes, powder can be selectively deposited in regions of the build area. We show that the applied voltage can be varied to affect the gradient between two materials, potentially leading to increased bonding between the materials. This suggests that ESPS can be used for multi-material LPBF parts with arbitrary 3-dimensional gradients.
9:35 AM
In-situ Reinforcement Processing for Laser Powder Bed Fused Ti64 Parts: Aditya Krishna Ganesh Ram1; Ahmet Tanrikulu1; Oscar Valdez Loya1; Paul Davidson1; Amirhesam Amerinatanzi1; 1University of Texas at Arlington
The objective of this study was to investigate how the microstructure and mechanical properties of Ti-6Al-4V samples, fabricated using laser powder bed fusion (L-PBF), change when a predefined local double melting strategy is employed within each layer of the manufacturing process. The analysis primarily focused on evaluating microstructural aspects, defects, and grain size, along with the mechanical properties, specifically the Vickers hardness at various positions within the samples. The findings indicated that the integration of the predefined locally double melting scan in each layer had a significant influence on the microstructure, resulting in variations in grain size across different locations, as well as hardness values with variations of up to 10% across different areas. Moreover, these discoveries underscore the potential of employing the predefined locally double melting strategy in each layer to create fabricated components with distinctive behaviors, like composites, which could find applications in the aerospace industry.
9:55 AM Break
10:25 AM
Method to Balance Thermals for Multi-functional 3D MJF Printing: Aja Hartman1; Lihua Zhao1; 1HP Labs
HP’s Multi Jet Fusion (MJF) is a powder-based additive manufacturing technology that selectively melts polymer powder, in a layer-by-layer fashion to create 3D parts. There are several different voxel properties that can be modulated using MJF including multi-color, ductility, conductivity, among others. Creating mechanically uniform multi-material parts with varying voxel properties throughout is challenging due to the liquid creating a competing cooling and active absorbing components that effect the temperature of printed parts differently. Here, we balance fusibility by utilizing a thermal imaging and an agent loading sweep thermal profile characterization print for each individual agent. We then digitally control the agent loading based on this data set and dynamic thermal imaging to produce a uniform temperature profile. This ensures even fusing throughout multi-agent printed parts, shown by uniform weight measurements of multi-color cubes from average weight 1.4±0.2 g to 1.5±0.1 g.
10:45 AM
Parametric Study of Processing of Ti6Al4V with Multiple 450 nm Diode Lasers: Halil Caglar1; Anqi Liang1; Kamran Mumtaz1; 1The University of Sheffield
Diode Area Melting (DAM) presents an alternative approach to traditional Laser Powder Bed Fusion (LPBF) approaches, integrating multiple individually addressable low-power fibre-coupled diode lasers into a laser head, these traverse across a powder bed to melt powdered feedstock. DAM research to date has focused on using low-power 808nm lasers to process Ti6Al4V (Ti64) powder. This work focuses on using multiple short wavelength 450nm 3W lasers to process Ti64 feedstock. It was found that when processing Ti64, absorption was 11% higher using 450nm lasers when compared to using 808 nm lasers and 14% higher than 1064nm lasers. This work demonstrated the potential to use shorter wavelength lasers in DAM/LPBF for improved melting efficiency and also it aimed to examine the impact of 450nm diode lasers on Ti64 and generate a parameter map for this material.
11:05 AM
Use of a Vibrating Build Platform during Powder-bed Fusion of Metals Using a Laser Beam: Nick Hantke1; Tobias Grimm1; Jan Sehrt1; 1Ruhr University Bochum
Powder-bed fusion of metals using a laser beam (PBF-LB/M) is an additive manufacturing technique with rising interest in industry and academia. One major topic of current research is to optimize the performance of parts manufactured by PBF-LB/M. The use of vibrations during the solidification of metals to improve their mechanical properties is well-known for metal casting and directed energy deposition. In this work, a vibrating build platform was used during the PBF-LB/M process to influence the microstructure of parts. Analyses show an increase in sample hardness by up to 12.3 % for the same process parameters. Especially for process parameters that produce parts with lower relative densities, vibrations have an influence on part density. With an increase in part density, this effect gets less pronounced
11:25 AM
Thin Wall Manufacturing in Laser Powder Bed Fusion for Heat Exchanger Applications: Evren Yasa1; Finlay Parson1; Anthony Molyneux1; James Whincup1; Ozgur Poyraz1; James Hughes1; 1Advanced Manufacturing Research Center, University of Sheffield
Laser Powder Bed Fusion (LPBF) has the highest technological maturity and industrial applicability among other metallic Additive Manufacturing (AM) processes due to its advantages such as enabling very complex geometries, a fine feature resolution and a good surface quality. Those benefits make LPBF very suitable especially for heat exchanger applications with intricate features, which are otherwise impossible or very costly to manufacture. To enable complex heat exchanger geometries by LPBF, thin wall manufacturing in various orientations is necessary with a good surface integrity which necessitates process parameters optimized in a different manner than bulk part manufacturing. This study aims at understanding the impact of various process parameters such as scan speed (1050-1950 mm/s) and laser power (280-480 W) as well as scan strategies like contour scanning and blocked path strategy on thin wall characteristics. These characteristics are demonstrated on S-curved walls addressing wall thickness and surface integrity.
11:45 AM
Open Architecture Control Software for Laser Powder Bed Fusion Machines: Justin Patridge1; Gabe Guss1; Saad Khairallah1; Amit Kumar1; Steven Hoover1; Ibo Matthews1; 1Lawrence Livermore National Laboratory
The modification of commercial machines and creation of custom systems furthers the development of the laser powder bed fusion additive manufacturing process. Adding sensors, changing scanning hardware, or changing how commands are processed and passed to the scanner can be crucial in designing an effective experiment. Commercial machine control software are usually inflexible and machine manufactures are reluctant to make modifications. Our software provides a way for communicating with existing scanner APIs and interfacing with the existing PLCs and other hardware on systems. Furthermore, the software provides a flexible GUI that is setup for a variety of powder bed machine layouts. We will outline our standardized architecture that limits the amount of machine specific code necessary to control a system.Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52-07NA27344.